FAMED British chef Marco Pierre White – star of NBC’s upcoming reality cooking show “The Chopping Block” – was turned away from the Rainbow Room the other night. The reason? His trademark Vans slip-on sneakers. Despite being decked out in his custom-tailored, $7,000 Saville Row best, White was not allowed into the restaurant, where the dress code requires jackets and “no jeans, sneakers, or T-shirts.”